Operational Technologies Corp. (OpTech) proposes to develop DNA aptamers against ten or more phosphorylated peptides from NCI's list of proteomic targets. These aptamers will be biotinylated and coupled to streptavidin-coated magnetic microbeads (MBs) or covalently bound to MBs, if necessary. The aptamer-MB reagents will be used to bind and enrich for their specific peptides in chaotrope and trypsin-treated human plasma and serum. Aptamer-MB reagents should be directly transferred to systems such as SISCAPA (Stable Isotope Standards and Capture by Anti-Peptide Antibodies), but will have the advantage of: 1) grater lot-to-lot reproductivity because aptamer DNA sequences will be known and reproduced with very high fidelity, 2) lower cost and faster development than comparable immunomagnetic reagents, 3) potentially greater affinity and specificity versus most antibodies. Aptamer-MBs can then release captured peptides by heating or acidification for mass spectral analyses in high throughput proteomic systems. OpTech will also attempt to precipitate target peptides from serum or plasma by chemically linking different aptamers at their ends to develop bi- and tridentate aptamers capable of linking peptides to form insoluble matrices. In Phase 2, OpTech will refine and expand the technology to include as may aptamers for peptide targets as possible for high-throughput proteomic use.